The present techniques relate generally to improving the environmental impact of chemical plants. More particularly, the present techniques relate to a method and a system for generating energy by utilizing flare gas to power a reciprocating engine generator.
This section is intended to introduce the reader to aspects of art that may be related to aspects of the present techniques, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present techniques. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
Chemical plants and refineries, hereinafter referred to as plants, often work with materials that may be explosive, flammable or toxic. The atmospheric discharge of these gases may be undesirable. To dispose of these gases without atmospheric discharge, most plants use a flare to combust or otherwise destroy the gases.
Flares are typically tall stacks located in a remote area in plants. Flares generally have a flame located at the tip for burning waste gas. Flare systems typically include the flare and the associated piping coupling the flare to vessels in the plants. Gases that may be discharged from process vessels within the plant are typically carried by the piping of the flare system to the flare. The gas is burned in the flame at the top of the flare stack, avoiding the free discharge of the gas into the atmosphere.
The flame of a flare system is typically kept continuously burning at the tip of the flare to ignite or destroy any gases that are pushed from the system to the flare. To keep this flame burning and to prevent stagnant areas in the flair header, a substantial amount of flammable gas is fed into the flare system. This flammable gas may be a mixture of methane and other light hydrocarbons termed fuel gas. The fuel gas increases the energy content of the gas in the flare system to offset any non-flammable gases, such as nitrogen, that have also been discharged to the flare. Generally, a minimum energy content of 300 British Thermal Units per standard cubic feet (BTU/SCF) of gas combusted by the flare is maintained to comply with regulations that permit a plant to assume a 98% efficiency for the burn.
The mixture of fuel gas with the other gases discharged from the process into the flare system may be termed flare gas. Flare gas may include gases, vapors, vaporizing liquid and so on, and may represent a significant energy loss for a plant. Accordingly, techniques to recover this energy may provide savings for a chemical plant.